CBS (Cell Broadcast Service) is used for emergency information delivery in a mobile network today. The CBS sends emergency information through broadcast to mobile phone terminals located in a target area to deliver the emergency information. Further, ETWS (Earthquake and Tsunami Warning System) is specified for more rapid disaster alert and more flexible delivery area.
For example, the rapid disaster alert is achieved by separately delivering two types of signals: a first report that delivers the most urgent minimum information such as “earthquake occurred” in the quickest way and a second report that delivers additional information such as a seismic intensity and an epicenter.
Further, the flexible delivery area is achieved by selectively using a delivery area according to three levels: Cell level, TA (Tracking Area) level and EA (Emergency Area) level.
Regarding the flexible delivery area, Patent Literature 1 discloses a technique that specifies a delivery area of an emergency message in units of wide areas or in units of sectors.